Problem on updating Projeqtor (rollback needed)

Hello,

For some reason, we have a problem on our Projeqtor since 9.1.3
We have done absolutely nothing in changing anything file related, or something that would pose problem (in our eyes)
But when i tried to update to 9.1.4 (and today, to 9.1.5, because waiting for next update just in case can help), i get the login screen after update like usual, but when i lo with my administrator account to initialise and open the app, i get this:

 

Do you have any idea what could cause this ?

Are there specific logs we should look into ?

Thank you

I don't quite understand where exactly is the specific log needed on the apache server, but this is what I found for June 4th when i updated it

 

If this is not this one, which one should it be ?

Thank you

Thank you,

After finding it and doing a test on another Vm we made just for this, which was in 8.3.3

I updated it to 9.0.6 without any problem
Then, when i tried to update to 9.1.5, i encountered the same problem i talked about above

I then made sure it was this log by trying to connect and looking at the modification date

 

Thank you